/*********************************************************************
 * Copyright (C) 2002 Andrew Khan
 * <p>
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.
 * <p>
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 * <p>
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
 ***************************************************************************/

package jxl.write.biff;

import jxl.biff.IntegerHelper;
import jxl.biff.Type;
import jxl.biff.WritableRecordData;

/**
 * Indicates an extension to the Shared String Table.  Currently this
 * contains blank records
 *
 * Thanks to Guenther for contributing a proper implementation of the EXTSST
 * record, replacing my previous dummy version
 */
class ExtendedSSTRecord extends WritableRecordData {
    private static final int infoRecordSize = 8;
    private int numberOfStrings;
    private int[] absoluteStreamPositions;
    private int[] relativeStreamPositions;
    private int currentStringIndex = 0;

    /**
     * Constructor
     *
     * @param numstrings the number of strings per bucket
     * @param streampos the absolute stream position of the beginning of
     * the SST record
     */
    public ExtendedSSTRecord(int newNumberOfStrings) {
        super(Type.EXTSST);
        numberOfStrings = newNumberOfStrings;
        int numberOfBuckets = getNumberOfBuckets();
        absoluteStreamPositions = new int[numberOfBuckets];
        relativeStreamPositions = new int[numberOfBuckets];
        currentStringIndex = 0;
    }

    public int getNumberOfBuckets() {
        int numberOfStringsPerBucket = getNumberOfStringsPerBucket();
        return numberOfStringsPerBucket != 0 ?
                (numberOfStrings + numberOfStringsPerBucket - 1) /
                        numberOfStringsPerBucket : 0;
    }

    public int getNumberOfStringsPerBucket() {
        // XXX
        // should come up with a more clever calculation
        // bucket limit should not be bigger than 1024, otherwise we end
        // up with too many buckets and would have to write continue records
        // for the EXTSST record which we want to avoid for now.
        final int bucketLimit = 128;
        return (numberOfStrings + bucketLimit - 1) / bucketLimit;
    }

    public void addString(int absoluteStreamPosition,
                          int relativeStreamPosition) {
        absoluteStreamPositions[currentStringIndex] =
                absoluteStreamPosition + relativeStreamPosition;
        relativeStreamPositions[currentStringIndex] = relativeStreamPosition;
        currentStringIndex++;
    }

    /**
     * Gets the binary data to be written out
     *
     * @return the binary data
     */
    public byte[] getData() {
        int numberOfBuckets = getNumberOfBuckets();
        byte[] data = new byte[2 + (8 * numberOfBuckets)];
        // number of strings per bucket
        IntegerHelper.getTwoBytes(getNumberOfStringsPerBucket(), data, 0);

        for (int i = 0; i < numberOfBuckets; i++) {
            // absolute stream position
            IntegerHelper.getFourBytes(absoluteStreamPositions[i],
                    data,
                    2 + (i * infoRecordSize));
            // relative offset
            IntegerHelper.getTwoBytes(relativeStreamPositions[i],
                    data,
                    6 + (i * infoRecordSize));
            // reserved
            // IntegerHelper.getTwoBytes(0x0, data, 8 + (i * infoRecordSize));
        }

        return data;
    }
}

